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Remote link for GMRS


haneysa
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I have a mountain that is 3.28 miles away, and 1444 feet above my home elevation (2145 ft) that is a possible location for a GMRS repeater. If I can work that out for local coverage (family & community EMCOMMS), I would also like to use the tower to mount a remote station in order to hit a GMRS repeater that is 138 miles from "my" mountain. The reason for wanting this capability is because the distant repeater covers my brother's house (165 miles from my house). My idea is to have a high-gain Yagi pointed at the distant repeater connected to a base station radio at the tower, and somehow RF link using two additional Yagis to my home station.

 

I have hit the distant repeater from a state park near me on my mobile (160 miles, 4500' ASL)....the distant repeater is about 5500' ASL.

 

I can think of several ways to do this that are most likely not within the letter of the Part 95 rules, but I am wondering if anyone can suggest a way to do so within part 95 limitations.

 

Yes, I am lobbying my brother to get his Technician license, and if he does so,the GMRS link would be rendered unnecessary. 

 

Thank you for any advice.

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Is there clear line of sight between the two points? Would need line of sight. Could use 2.4Ghz wifi bridge. Use two 3 or  4 foot dish antennas.

You could have someone who installs and license's microwave links to do a "path study" on the link path between the two sites. 

There are many repeater that are linked by internet. That would be the most cost effective.

My 2 cents at my knowledge level.

WRCW870

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160 miles is really, really long for a RF link. The speed-of-light delay alone (850us) is problematic for 802.11-based linking. An Internet link through Asterisk would be much easier and much more reliable. There's a lot of tutorials on how to set up private Asterisk links, and the final architecture will strongly resemble an AllStarLink node.

 

Internet-based linking is permissible for operating a remote base per 2017 FCC rule update.

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I have clear LOS between my house and the near mountain top where I hope to install a tower. The near mountain is only a few miles away. I will do research on the microwave link. I was wondering if wifi with two yagis would work. This project is a year or more out, if it ever even comes to pass.

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I think what original poster is looking for, is not a wifi or microwave link, but a way to hit a GMRS repeater on 467.xxx MHz, that is located 138 miles away.

I say, go for it! People do Earth-Moon-Earth all the time, and that's 500,000 miles roundtrip, and there are no repeaters on Moon just yet. 138 miles should be doable if there is a line of sight between mountains. And it appears that you have done it already (the hitting the remote repeater).

 

And regarding Part 95 letter ad spirit, I do not see why can't you locally retransmit what you hear from the distant repeater. The so-called "shotgun" repeater link was discussed on this forum before.

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I was thinking WiFi for the repeater remote control.  Not for internet relay of GMRS.  As far as point-to-point radio relay of the two repeaters, I agree... go for it. 

 

Unless there is something I am missing in the statutory code, the transmitter output power of a repeater is limited to 50 Watts, but there is no limit to ERP.  If you build/buy a +20dbg directional antenna, you're able to get close to 5,000 watts ERP.  With enough elevation, you should be able to talk to someone in Texas from Washington, DC.

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Food for thought.

 


 

I have done long range wifi with a set of $3000 ubiquity air fiber dual dish +45db gain set up, 41 miles is as far as I got. Internet is the best option over a 100 miles. You can't dispute the science of a link this long, telcos used huge feed horns 20' wide, 200' in the air and 6" wave guide with over a million in infrastructure to build and maintain a single microwave links 100 miles. The FCC won't licence a path that long. I link several sites together using cellular internet, at 15 bucks a site it will take years to over come the cost of a WIFI or microwave link. Don't waste your money, trust the science, 160 mile link cost effectively is a total pipe dream..... If you do the math the aiming of a link 160 miles apart would need to have an accuracy of .005 of an inch or roughly the width of a human hair, good luck maintaining that with wind and interference along the path.

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It seems to me the central challenge is to use the tower to mount a remote station in order to hit a GMRS repeater that is 138 miles from "my" mountain. ​In other words place a remote controlled station on the mountain top to talk to the remote repeater.  The secondary issue is how to get from "home" to the local mountain top.

 

For this task it seems you could just link the two stations using GMRS simplex. Technically this would be a remote controlled fixed station and subject to the 15 watt transmitter output power limit. The use of highly directional antennas would be ok since the limitation is on output power rather than ERP.  Any of the 462/467 main (25kHz) main channels could be used.  

 

If you mount a repeater on the local mountain top you would just use standard linking procedures (depends on the repeater controllers you use) to tie the two together. Each repeater would then have two-inputs and would operate when either was active but only transmit on the link whenever the local input was active. You could use any 462 mHz or 467mHz main frequency. Though, 467 would probably work better to avoid desense from the local transmitter.  You could also create a full-duplex link with each repeater listening to the other repeater's output (different channel pairs of course). But, that would require an additional duplexer and would probably be overkill in this application.

 

If you do not install a repeater then you would need to create a remote-controlled base/fixed station on your local mountain top. You could then use GMRS or Wi-Fi for the link from your home to the remote-controlled station.  However, A remote controlled station is already, in essence, a repeater so it is probably best to just build the local repeater and then add the linking,

 

CAVEAT: This approach will work well in a rural or sparsely populated area. But, in an urban environment you might have occasional to continual co-channel interference.

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